Adapted from: Classic Southern Desserts
Whisk milk and egg yolks in a bowl and pour into a heavy saucepan. Add sugar, flour, and salt and whisk together until smooth. Cook over medium heat, stirring constantly, 20 minutes or until thickened. If it’s not getting as thick as you’d like after 20 minutes, feel free to add another teaspoon of flour. Remove from heat; stir in the vanilla.
Arrange one-third of vanilla wafers in bottom of a small serving dish. Slice 1 banana and layer over wafers. Spoon one-third of custard over bananas. Repeat until custard is gone and you have a few solid layers.
Beat whipping cream at medium speed with an electric mixer until foamy; gradually add powdered sugar to mixture, beating until soft peaks form. Spread over custard. Serve immediately or cover and chill for eight hours.